package org.apache.solr.util;

import java.io.IOException;
import java.io.Writer;

/** Single threaded BufferedWriter
 *  Internal Solr use only, subject to change.
 */
public class FastWriter extends Writer {
    // use default BUFSIZE of BufferedWriter so if we wrap that
    // it won't cause double buffering.

    private static final int BUFSIZE = 8192;
    protected final Writer sink;
    protected char[] buf;
    protected int pos;

    public FastWriter(Writer w) {
        this(w, new char[BUFSIZE], 0);
    }

    public FastWriter(Writer sink, char[] tempBuffer, int start) {
        this.sink = sink;
        this.buf = tempBuffer;
        this.pos = start;
    }

    public static FastWriter wrap(Writer sink) {
        return (sink instanceof FastWriter) ? (FastWriter) sink : new FastWriter(sink);
    }

    @Override
    public void write(int c) throws IOException {
        write((char) c);
    }

    public void write(char c) throws IOException {

        if (pos >= buf.length) {
            flush(buf, 0, pos);
            pos = 0;
        }
        buf[pos++] = c;
    }

    @Override
    public FastWriter append(char c) throws IOException {

        if (pos >= buf.length) {
            flush(buf, 0, pos);
            pos = 0;
        }
        buf[pos++] = c;
        return this;
    }

    @Override
    public void write(char arr[], int off, int len) throws IOException {

        for (;;) {
            int space = buf.length - pos;

            if (len <= space) {
                System.arraycopy(arr, off, buf, pos, len);
                pos += len;
                return;
            }
            else if (len > buf.length) {
                if (pos > 0) {
                    flush(buf, 0, pos);  // flush
                    pos = 0;
                }
                // don't buffer, just write to sink
                flush(arr, off, len);
                return;
            }

            // buffer is too big to fit in the free space, but
            // not big enough to warrant writing on its own.
            // write whatever we can fit, then flush and iterate.

            System.arraycopy(arr, off, buf, pos, space);
            flush(buf, 0, buf.length);
            pos = 0;
            off += space;
            len -= space;
        }
    }

    @Override
    public void write(String str, int off, int len) throws IOException {

        for (;;) {
            int space = buf.length - pos;

            if (len <= space) {
                str.getChars(off, off + len, buf, pos);
                pos += len;
                return;
            }
            else if (len > buf.length) {
                if (pos > 0) {
                    flush(buf, 0, pos);  // flush
                    pos = 0;
                }
                // don't buffer, just write to sink
                flush(str, off, len);
                return;
            }

            // buffer is too big to fit in the free space, but
            // not big enough to warrant writing on its own.
            // write whatever we can fit, then flush and iterate.
            str.getChars(off, off + space, buf, pos);
            flush(buf, 0, buf.length);
            pos = 0;
            off += space;
            len -= space;
        }
    }

    @Override
    public void flush() throws IOException {

        flush(buf, 0, pos);
        pos = 0;
        if (sink != null) {
            sink.flush();
        }
    }

    public void flush(char[] buf, int offset, int len) throws IOException {
        sink.write(buf, offset, len);
    }

    public void flush(String str, int offset, int len) throws IOException {
        sink.write(str, offset, len);
    }

    @Override
    public void close() throws IOException {

        flush();
        if (sink != null) {
            sink.close();
        }
    }

    public void flushBuffer() throws IOException {

        flush(buf, 0, pos);
        pos = 0;
    }
}
